HVAC systems can be used to regulate the environment within an enclosed space. Typically, an air blower is used to pull air from the enclosed space into the HVAC system through ducts and push the air back into the enclosed space through additional ducts after conditioning the air (e.g., heating, cooling or dehumidifying the air). Various types of HVAC systems, such as roof top units, may be used to provide conditioned air for enclosed spaces.
A common type of air blower that is used to move air through an HVAC system is a belt-driven centrifugal scroll fan. The centrifugal scroll fan includes an impeller that is rotated by a motor via a belt to create system pressure in a HVAC unit and move the air. With the centrifugal scroll fan, there is a scroll with a circular-shape that surrounds the impeller and directs the air to a particular discharge point.
Another type of air blower that is used in HVAC systems is a plug fan. A plug fan includes an open blower wheel with exposed blades that are rotated by a motor. Typically, plug fans are installed within a fan plenum of an HVAC unit when used thereby. The motor is often a direct drive motor that rotates the blower wheel to discharge air in a 360 degree pattern and create system pressure to move air. Plug fans can operate quieter than centrifugal scroll fans since air is discharged radially instead of being forced into a single discharge point by a scroll. Additionally, since plug fans are typically fixed within a fan plenum, the insulation of the plenum can also assist in reducing fan noise.
Unfortunately, locating the plug fan within the fan plenum reduces access for maintenance. Additionally, the open blower wheel creates a danger to maintenance technicians once access to the plug fan is finally obtained. System pressure may also suffer due to the open blower wheel design.